In North America, tractor lubricants are often referred to as Universal Tractor Transmission Oils (“UTTO”) or Tractor Hydraulic Fluids (“THF”). These lubricants provide performance required for hydraulics, transmission, gears, power take-off (“PTO”), and wet-brakes. In international and emerging markets, Super Tractor Universal Oil (“STUO” or “STOU”) lubricants are more widely used. STUO lubricants provide satisfactory lubrication of diesel and gasoline engines, in addition to providing the performance required for hydraulic, transmission, gear, PTO, and wet brake systems.
To meet these varied requirements, tractor lubricants must balance a large number of performance properties. UTTO and STUO tractor lubricants must provide anti-wear, provide load-carrying protection, and control frictional characteristics for equipment durability. In addition, the STUO tractor lubricants must maintain basic engine performance, without compromising the requirements of THFs for wet brake, PTO, transmission, gear, and hydraulics performance. Many of the additives used in tractor lubricant formulation are multifunctional and there is often a conflict generated between properties. To ensure that the tractor lubricant operates over a wide temperature range, it is necessary for the oil to be multi-grade. This requires the use of carefully chosen base oils combined with viscosity index improvers and pour point depressants to achieve the low and high temperature viscosity limits.
These conflicts inevitably mean that additives must be carefully selected and balanced. There thus, exists a need for a low phosphorous-based STUO, which maintains good antiwear and extreme pressure protection required for gear, transmission, and hydraulic performance. In addition, having a lower treat rate additive package may reduce additive shipping costs, improve plant through-put, and provide economic benefits to lubricant blenders in terms of lower net additive treat costs.